Multi-frequency RFID apparatus and methods of reading RFID tags

Abstract

A portable/handheld device is provided having a processing module configured to selectively operate a reading mode selected from a far-field mode and a near-field mode, and a directional antenna array coupled to the processing module. The directional antenna array includes a first antenna element configured to radiate electromagnetic (EM) radiation in a far-field, and a second antenna element coupled to the first antenna element. The second antenna element is configured to radiate EM radiation in a near-field. The second antenna element includes an antenna transducer configured to selectively cancel far-field EM radiation from the first antenna element. A method of reading inductively coupled radio frequency identification (RFID) tags is also provided having the steps of scanning at least one frequency band to detect a RFID tag, and selectively radiating one of a near-field electromagnetic (EM) field and a far-field EM field based on the detected RFID tag.

What is claimed is: 
     
       1. A portable/handheld device, comprising:
 a processing module configured to selectively operate a reading mode selected from a far-field mode and a near-field mode; and 
 a directional antenna array coupled to said processing module, said directional antenna array comprising:
 a first antenna element configured to radiate electromagnetic (EM) radiation in a far-field; and 
 a second antenna element coupled to said first antenna element, said second antenna element configured to radiate EM radiation in a near-field, said second antenna element comprising an antenna transducer configured to selectively cancel far-field EM radiation from said first antenna element. 
 
 
     
     
       2. A portable/handheld device according to  claim 1 , wherein said portable/handheld device is a radio frequency identification (RFID) interrogator. 
     
     
       3. A portable/handheld device according to  claim 1 , wherein said first antenna element and said second antenna element are both configured to radiate EM radiation substantially away from said processing module. 
     
     
       4. A portable/handheld device according to  claim 1 , wherein said first antenna element comprises a driven element and a parasitic element separated from said driven element, said parasitic element comprises at least one element selected from a reflector element and a director element. 
     
     
       5. A portable/handheld device according to  claim 4 , wherein a first element of said at least one element of said parasitic element is configured to resonate at about 915 MHz; and
 wherein said second antenna element is configured to resonate at a frequency selected from 125 kHz and 13.56 MHz. 
 
     
     
       6. A portable/handheld device according to  claim 5 , wherein a second element of said at least one element of said parasitic element is configured to resonate at a frequency selected from about 2.45 GHz and about 5.6 GHz. 
     
     
       7. A portable/handheld device according to  claim 4 , wherein said antenna transducer of said second antenna element comprises at least one conductive current loop. 
     
     
       8. A portable/handheld device according to  claim 7 , wherein said at least one conductive current loop encircles a perimeter of one of said at least one element of said parasitic element. 
     
     
       9. A portable/handheld device according to  claim 7 , wherein said antenna transducer of said second antenna element comprises a first conductive current loop and a second conductive current loop spaced apart from said first conductive current loop, each of said first conductive current loop and said second conductive current loop encircles an axis of a largest dimension of said parasitic element, said first conductive current loop and said second conductive current loop together configured to create far-field cancellation. 
     
     
       10. A portable/handheld device according to  claim 5 , wherein said second element of said at least one element of said parasitic element comprises at least one of a 2.45 GHz radiating element and a 5.6 GHz radiating element. 
     
     
       11. A portable/handheld device according to  claim 5 , wherein said at least one element of said parasitic element is selected from a slotted antenna, a dipole element, a printed circuit patch antenna element, and a monopole antenna element. 
     
     
       12. A portable/handheld device according to  claim 1 , wherein said first antenna element comprises an array of radiating elements, said array of radiating elements configured as one of parasitically-driven, partially all-driven, and all-driven, said array of radiating elements further configured to operate in at least one frequency selected from about 2.45 GHz and about 5.6 GHz. 
     
     
       13. A portable/handheld device according to  claim 12 , wherein said array of radiating elements is configured to radiate a beam, said processor module is further configured to electronically steer said radiated beam. 
     
     
       14. A portable/handheld device according to  claim 1 , wherein one of said first antenna element and said second antenna element is an array of slotted antennas, each of said array of slotted antennas having a different size based on a different frequency of operation. 
     
     
       15. A portable/handheld device according to  claim 1 , wherein one of said first antenna element and said second antenna element is an array of slotted antennas, each of said array of slotted antennas having a similar size. 
     
     
       16. A portable/handheld device according to  claim 2 , wherein said processor module is further configured to scan frequency bands for RFID tags. 
     
     
       17. A portable/handheld device according to  claim 2 , wherein said processor module is further configured to:
 designate user-selected frequency bands; and 
 scan said user-selected frequency bands for RFID tags. 
 
     
     
       18. A multi-frequency radio frequency identification (RFID) device, said device comprising:
 a processor configured to scan frequency bands for RFID tags and select a reading mode frequency band based on said scanned frequency bands; 
 a switch coupled to said processor, said switch configured to select at least one reading mode frequency band; 
 a first antenna element coupled to said processor, said first antenna element configured to radiate electromagnetic (EM) radiation in a far-field; and 
 a second antenna element coupled to said first antenna element, said second antenna element configured to radiate EM radiation in a near-field, said second antenna element comprising an antenna transducer configured to selectively cancel far-field EM radiation from said first antenna element, one of said first antenna element and said second antenna element further configured to resonate at said at least one reading mode frequency band. 
 
     
     
       19. A multi-frequency RFID device according to  claim 18 , wherein said first antenna element comprises a driven element and a parasitic element separated from said driven element; and wherein said antenna transducer of said second antenna element is coupled to said parasitic element. 
     
     
       20. A multi-frequency RFID device according to  claim 19 , wherein said parasitic element comprises at least one element selected from a reflector element and a director element. 
     
     
       21. A multi-frequency RFID device according to  claim 18 , wherein said antenna transducer of said second antenna element comprises a first conductive current loop, said first conductive current loop encircles a perimeter of one of said at least one element of said parasitic element. 
     
     
       22. A multi-frequency RFID device according to  claim 21 , wherein said antenna transducer of said second antenna element further comprises a second conductive current loop spaced apart from said first conductive current loop, each of said first conductive current loop and said second conductive current loop encircles an axis of a largest dimension of said parasitic element. 
     
     
       23. A multi-frequency RFID device according to  claim 22 , wherein said first conductive current loop is substantially parallel to said second conductive current loop, said first conductive current loop and said second conductive current loop are configured to conduct current in a first direction. 
     
     
       24. A multi-frequency RFID device according to  claim 21 , wherein said antenna transducer of said second antenna element further comprises a second conductive current loop spaced apart from said first conductive current loop; and
 wherein said parasitic element comprises a first lobe and a second lobe spaced apart from said first lobe, said first conductive current loop encircling said first lobe, and said second conductive loop encircling said second lobe. 
 
     
     
       25. A multi-frequency RFID device according to  claim 20 , wherein one of said at least one element of said parasitic element is configured to resonate at a frequency of about 915 MHz and said second antenna element is configured to resonate at a frequency selected from about 125 kHz and about 13.56 MHz. 
     
     
       26. A multi-frequency RFID device according to  claim 25 , wherein one of said at least one element of said parasitic element is configured to resonate at a frequency selected from about 2.45 GHz and about 5.6 GHz. 
     
     
       27. A multi-frequency RFID device according to  claim 18 , wherein said first antenna element is further configured to radiate a directional pattern having substantially less than 180 degrees of directivity. 
     
     
       28. A multi-frequency interrogator antenna assembly comprising:
 an array of radiating elements, said array of radiating elements configured as one of parasitically-driven, partially all-driven, and all-driven and configured to selectively radiate electromagnetic (EM) radiation in at least one of a near-field and a far-field based on a frequency of a detected RFID tag; and 
 a transducer configured to cancel said far-field EM radiation when selectively radiating in said near-field, the near-field EM radiation being one of about 135 kHz and about 13.56 MHz, and the far-field EM radiation being one of about 915 MHz, about 2.45 GHz, and about 5.6 GHz. 
 
     
     
       29. A multi-frequency interrogator antenna assembly according to  claim 28 , wherein said array of radiating elements comprises:
 a first radiating element configured to resonate at one of about 2.45 GHz and about 5.6 GHz; 
 a second radiating element configured to resonate at one of about 135 kHz and about 13.56 MHz; and 
 a third radiating element configured to resonate at about 915 MHz. 
 
     
     
       30. A multi-frequency interrogator antenna assembly according to  claim 28 , wherein each radiating element of said array of radiating elements is selected from a slotted antenna, a dipole element, a patch antenna element, and a monopole antenna element.